restoring my Canadian 71 Dart 340 Swinger Special

It looks like a complete return to original would be a much larger task. Replacement of frame rails, removal and repair to areas where subframe connectors and back half components are installed. Most of the value of this car (in my opinion) is tied to what is on the data plate. If your intention is not to return it to original for that reason, I would change what you need to in order to suit your desire and go for it.